JPH11285849A - Device for detecting position of electrode for spot welding machine, its detecting method and its correcting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correctly correct the wear of an electrode by providing a position detector in cooperation with a sensor to detect an arbitrary position of a movable electrode relative to a welding gun to correctly detect the position of the electrode of the welding gun. SOLUTION: An electrode position detector 1 comprises a welding gun 2 and a control system 5. A movable electrode 22 and a fixed electrode 24 are mounted on the welding gun 2. A feed mechanism 30 is mounted on an arm base part 20b and supported thereby. A servo motor 26 is mounted on the arm base part 20b to drive the feed mechanism 30. The movable electrode 22 can be moved in each feed direction of the feed mechanism 30. The fixed electrode 24 is mounted at the position opposite to the movable electrode 22 by an arm end part 20a. An electrode sensor 60 to function as a tip detector by fixing a bracket set to a gun arm 20 is built in the welding gun 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode position detecting device for a spot welding machine for accurately detecting an electrode position of a welding gun mounted on a robot and correcting an electrode wear amount, a detecting method thereof, and a correcting method therefor. .

[0002]

2. Description of the Related Art For example, a welding gun for performing spot welding of a vehicle body has a movable electrode driven by a servomotor and a fixed electrode fixed to a gun body. At the time of spot welding, an object to be welded is sandwiched between the fixed electrode and the fixed electrode by moving the movable electrode toward the fixed electrode, and the spot welding is performed by energizing in this state.

[0003] In the case of a welding gun using a servomotor, the pressing force on the workpiece is indirectly controlled at the stop position of the movable electrode. As a result, the stop position of the fixed electrode with respect to the workpiece changes, and if the stop position is the same, the pressing force at the time of spot welding is gradually reduced, and the welding quality is adversely affected. For this reason, it is necessary to detect the wear amount of both electrodes and correct the stop position of the fixed electrode by the wear amount. Conventionally, in order to make this correction, the wear of the electrodes is detected as follows. (1) Method of installing a limit switch on a fixed block of the wear amount detecting jig 10 (see FIG. 14) First, the entire robot is operated to the measurement position, and the limit switch of the wear amount detecting jig 10 is turned on at the tip of the movable electrode. Let it. Then, the position data of each axis of the robot at this time is captured. Next, the same operation is performed for the fixed electrode.
Then, these position data are compared with the position data of a new electrode, and the wear amount of each of the movable electrode and the fixed electrode is calculated. Finally, the position data of each axis of the robot is corrected according to the wear amount of both electrodes (see the flowchart of FIG. 17). (2) A method in which a movable electrode is brought into contact with a fixed block to detect that the electrode tip touches from a change in the current value of the servomotor (see FIG. 15). First, the entire robot is operated to a measurement position and the servomotor is driven. Then, the movable electrode is brought into contact with the fixed block. Then, from the change in the current value of the servomotor at this time, it is detected that the tip of the electrode has contacted the fixed block (FIG. 1).
6), when the contact state is detected, the position data of the movable electrode shaft is taken in. Further, the servo motor is driven to hold the workpiece with the movable electrode and the fixed electrode. It is detected from the change in the current value of the servomotor at this time that the work to be welded is added, and when the contact state is detected, the position data of the movable electrode shaft is taken in. These position data are compared with the position data of a new electrode, and the wear amount of each of the movable electrode and the fixed electrode is calculated. Finally, the position data of each axis of the robot is corrected according to the wear amount of both electrodes (see the flowchart of FIG. 18).

In this case, the contact of the electrode with the fixed block is detected by the axial movement of the movable electrode. However, the position of both the movable and fixed electrodes may be calculated by moving the entire robot.

[0005]

However, the above-mentioned conventional methods have the following disadvantages. In the case of the method (1), it is impossible to separate errors due to mechanical backlash or bending of the robot main body depending on rigidity and positioning repeatability. In addition, when the electrodes are replaced during the welding operation, the robot (gun body) must be moved from the operation position to the position of the wear amount detecting jig 10, which requires time for recovery. Further, a space for installing the wear amount detecting jig 10 is required, and the cost is increased. Also in the case of the method (2), it is not possible to separate errors due to mechanical backlash of the robot body, deflection depending on rigidity, and positioning repeatability. When the electrode is replaced during the welding operation, the robot (gun body) is moved from the operation position to the wear amount detecting jig 10.
And it takes time to recover to the welding operation. Further, a space for installing the wear amount detection jig 10 is required.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and is intended to accurately detect an electrode position of a welding gun and accurately correct an electrode wear amount. It is an object of the present invention to provide a device electrode position detecting device, a detecting method thereof, and a correcting method thereof.

[0007]

The present invention for achieving the above object is constituted as follows for each claim.

The invention according to claim 1 is an electrode position detecting apparatus for a spot welding machine applied to a spot welding machine in which a welding robot operates a welding gun having a pair of relatively movable welding electrodes by a welding robot. An arbitrary coordinate system is defined for the welding gun, and a sensor defined in the coordinate system for detecting a movable electrode moved to an arbitrary position and an arbitrary position of the movable electrode with respect to the welding gun are determined. It is characterized by having a position detector cooperating with the sensor to be detected.

According to a second aspect of the present invention, in the electrode position detecting device for a spot welding machine according to the first aspect, the sensor detects a tip portion of the movable electrode, and the arbitrary position of the movable electrode is detected. Is a tip of the movable electrode in the welding gun.

According to a third aspect of the present invention, in the electrode position detecting device for a spot welding machine according to the second aspect, the welding gun supports a feed mechanism for feeding a movable electrode in a feed direction and the feed mechanism. A gun arm having a base portion and an end portion that supports another welding electrode with respect to the movable electrode, wherein the sensor is fixed to the base portion of the gun arm and intersects the moving direction of the movable electrode. And a light receiver fixed to a base portion of the gun arm and receiving a light beam from the light emitter.

According to a fourth aspect of the present invention, in the electrode position detecting device for a spot welder according to the third aspect, the welding gun has one support piece supporting the light emitter and the other support piece supporting the light receiver. The gun arm further includes a pair of support pieces spaced apart from each other for supporting, and a bracket fixed to a base portion of the gun arm.

According to a fifth aspect of the present invention, in the electrode position detecting apparatus for a spot welder according to the first aspect, the position detector is fixed to the welding gun and feeds the movable electrode. A servo motor for driving the feed mechanism and a control device for controlling the servo motor and detecting the position of the movable electrode are provided.

According to a sixth aspect of the present invention, in the electrode position detecting device for a spot welding machine according to the fifth aspect, the control device is configured to detect a position of the movable electrode and the fixed electrode attached to the welding gun. It is characterized by recognizing the state of pressure contact.

According to a seventh aspect of the present invention, in the electrode position detecting apparatus for a spot welding machine according to the sixth aspect, the control device controls the feed of the feed mechanism, and the welding gun is controlled before the spot welding. A first feed in which the movable electrode moves to the arbitrary position between the movable electrode and the fixed electrode attached to the first feed, a second feed in which the movable electrode is in a non-pressurized contact state before spot welding; After the spot welding, a third feed in which the movable electrode moves to the arbitrary position, after the spot welding, a fourth feed in which the movable electrode is brought into a non-pressurized contact state,
Recognizing a deformation of one of the movable electrode and the fixed electrode based on at least two of the second, third, and fourth feeds.

According to an eighth aspect of the present invention, in the electrode position detecting device for a spot welding machine according to the seventh aspect, the control device controls a feed of a feed mechanism based on the deformation.

According to a ninth aspect of the present invention, in the electrode position detecting device for a spot welder according to the sixth aspect, the control device is configured to control the fixed electrode before the movable electrode enters a non-pressurized contact state. The method is characterized in that the movable electrode is controlled so as to generate a pressing force.

According to a tenth aspect of the present invention, in the electrode position detecting device for a spot welder according to the ninth aspect, one of the movable electrode and the fixed electrode is an electrode member connected to the feed mechanism. And an electrode tip mounted on the electrode member.

According to an eleventh aspect of the present invention, in the electrode position detecting device for a spot welding machine according to the ninth aspect, the control device controls a feed amount of the feed mechanism, and the movable electrode is not pressurized. A first feed amount to be in a contact state, a second feed amount in which the movable electrode acts on the fixed electrode and has a pressing force of a magnitude balanced with a reaction of the fixed electrode, and the movable electrode Bending of the welding gun based on a third feed amount, a first, a second, and a third feed amount that acts on the fixed electrode and moves so as to have a pressing force having a magnitude different from a magnitude balanced with the reaction of the fixed electrode. Is recognized.

According to a twelfth aspect of the present invention, in the electrode position detecting device for a spot welding machine according to the eleventh aspect, the control device controls a feed amount of a feed mechanism based on the bending. .

According to a thirteenth aspect of the present invention, in the electrode position detecting device for a spot welding machine according to the eleventh aspect, the control device is configured to control the first position of the welding gun having a first direction.
And recognizing the effect of the direction of the bending of the welding gun based on the second bending of the welding gun having a second direction different from the first direction and the first and second bendings of the welding gun. It is characterized by.

According to a fourteenth aspect of the present invention, in the electrode position detecting device for a spot welding machine according to the thirteenth aspect, the control device controls a feed amount of a feed mechanism based on the influence. .

According to a fifteenth aspect of the present invention, there is provided an electrode position detecting device for a spot welding machine applied to a spot welding machine in which a welding robot operates a welding gun having a pair of relatively movable welding electrodes. An arbitrary coordinate system is defined for the welding gun, a sensor means defined in the coordinate system for detecting a movable electrode moved to an arbitrary position, and an arbitrary position of the movable electrode with respect to the welding gun. And a position detecting means cooperating with the sensor means for detecting the position.

The invention according to claim 16 is a spot welding machine electrode position detecting method applied to a spot welding machine in which a welding robot operates a welding gun having a pair of relatively movable welding electrodes by a welding robot. A coordinate system is defined for the welding gun, a sensor is fixed to the coordinate system, a movable electrode moved to an arbitrary position is detected by the sensor, and an arbitrary position of the movable electrode on the welding gun is defined as the sensor. It is characterized by detection by a cooperating position detector.

According to a seventeenth aspect of the present invention, in the electrode position detecting method for a spot welder according to the sixteenth aspect, the detection by the sensor includes detecting a tip end of the movable electrode. The arbitrary position is a tip of the movable electrode with respect to a welding gun.

An invention according to claim 18 is an electrode position correcting method used for a welding gun of a type which is attached to a welding robot and drives a movable electrode by a servomotor, wherein the welding gun has a tip portion of the movable electrode. A first step of fixing and mounting a tip detector for detecting a position, and a step of attaching a new movable electrode and a fixed electrode to the welding gun and driving the movable electrode until the tip is detected by the tip detector. Two steps, a third step of calculating the amount of movement of the movable electrode from its original position until its tip is detected by the tip detector, and subsequently driving the movable electrode until it hits the fixed electrode. A fourth step of calculating the moving amount of the movable electrode from the original position to the abutting position when the pressing force of the movable electrode is reduced by reducing the pressing force of the movable electrode; Is performed, the movable electrode is moved from an original position to a position where the distal end is detected by the distal end detector, a sixth step of calculating the amount of movement, and then the movable electrode is driven until it hits the fixed electrode A seventh step of calculating the moving amount of the movable electrode from the original position to the abutting position when the pressing force is reduced by reducing the pressing force of the movable electrode, and a new moving electrode. A ninth step of calculating a wear amount of each of the movable electrode and the fixed electrode based on the obtained respective movement amounts and the respective movement amounts obtained by the movable electrodes after welding. .

According to a nineteenth aspect of the present invention, in the method for correcting an electrode position of a welding gun according to the eighteenth aspect, the fourth aspect is provided.
The operation of abutting the movable electrode against the fixed electrode performed in the step includes an operation of pressing both electrodes with a maximum pressing force within a maximum allowable pressing force of the welding gun obtained by the servomotor.

According to a twentieth aspect of the present invention, in the method for correcting an electrode position of a welding gun according to the eighteenth aspect, an electrode position correction method is used for a welding gun of a type which is attached to a welding robot and drives a movable electrode by a servomotor. The method, further comprising the step of correcting the position of the movable electrode during pressurization during welding based on the respective wear amounts of the movable electrode and the fixed electrode calculated in the ninth step. I do.

According to a twenty-first aspect of the present invention, there is provided an electrode position correcting method used for a welding gun of a type which is attached to a welding robot and drives a movable electrode by a servo motor, wherein the movable electrode is brought into contact with a fixed electrode. A first step of driving, a second step of pressing the movable electrode with a first set pressing force to calculate a movement amount of the movable electrode from an original position to an abutting position, and the first set pressing force A third stage in which both electrodes are pressurized again with a different pressing force, a fourth stage in which the amount of movement of the movable electrode from the original position to the abutting and pressing position is calculated, and the amount of movement to the abutting position And a fifth step of calculating the rigidity of the welding gun from the amount of movement to the abutting and pressing position.

According to a twenty-second aspect of the present invention, in the method for correcting an electrode position of a welding gun according to the twenty-first aspect, the fifth aspect of the present invention,
The method may further include correcting the position of the movable electrode when pressurizing during welding based on the rigidity of the welding gun calculated in the step.

According to a twenty-third aspect of the present invention, in the method for correcting an electrode position of a welding gun according to the twenty-first aspect, the first position correction method comprises:
The process from the stage to the fourth stage is performed, then, the posture of the welding gun is changed, and the first to fourth stages are again performed with the welding gun in the vertical posture, and the respective positions obtained by the respective postures are obtained. A step of calculating a stiffness in consideration of the weight of the gun from a movement amount.

According to a twenty-fourth aspect of the present invention, in the method for correcting an electrode position of a welding gun according to the twenty-third aspect, the movable electrode at the time of welding is determined based on the rigidity calculated in consideration of the weight of the welding gun calculated in the step. The method further comprises the step of correcting the position at the time of pressing.

[0032]

The present invention configured as described above has the following effects.

According to the first to fifteenth aspects of the present invention, it is possible to detect the position of both electrodes with high accuracy, including no mechanical backlash or bending depending on rigidity and an error due to positioning repeatability. Can be.

According to the inventions described in claims 16 and 17, the positions of the two electrodes, which do not include errors due to mechanical backlash and rigidity of the robot body and errors due to positioning repeatability, are detected with high accuracy. Can be.

According to the inventions described in claims 18 and 20, the robot body detects mechanical backlash and flexure depending on rigidity, and detects the amount of wear of both electrodes with high accuracy without errors due to positioning repeatability. can do.
Accordingly, since the electrode wear amount can be accurately corrected, further improvement in welding quality can be expected. Further, even if the electrode is replaced during the welding operation, the robot (welding gun main body) can be moved from the same operation position to a position where the pressure can be applied with a minimum pressure, so that the recovery time can be reduced. Furthermore, there is no need for a special space for installing the wear amount detecting device, and no cost is required.

In the invention according to claim 19, most of the electrodes used for welding are premised on frequent electrode replacement.
The electrode tip is attached in such a manner that a tapered cylindrical electrode tip is driven into an electrode holder that fits the electrode tip. Therefore, if the insertion of the electrode tip is not easy, the electrode tip will sink into the electrode holder each time pressurization is repeated, causing an error in the electrode wear amount measured in advance. Therefore, by pressurizing the electrode with the maximum allowable pressing force immediately before the detection of the electrode wear amount, the electrode tip can be sufficiently inserted, so that the electrode wear amount can be detected with high accuracy. Further, no error occurs in the electrode wear amount due to the subsequent pressurization. Therefore, since the electrode wear amount can be accurately corrected, further improvement in welding quality can be expected.

According to the twenty-first and twenty-second aspects of the present invention, it is possible to detect the amount of bending of the arm of the welding gun and to perform correction based on this detection, which could not be performed conventionally. For this reason, the optimal amount of deflection of the gun arm can be corrected in accordance with the pressing force, so that a further improvement in welding quality can be expected.

According to the twenty-third and twenty-fourth aspects of the present invention, it is possible not only to detect the amount of deflection of the gun arm and to perform correction based on the detection, but also to correct variations in electrode pressing force due to the gun posture. Since a desired electrode pressure can be accurately obtained, welding quality is stabilized.

[0039]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the drawings.

The spot welding apparatus generally used at present does not have a function (equalizing) for correcting a deviation between a pressing point and an object to be welded by itself. Therefore,
When welding an object to be welded, it is necessary that the fixed electrode is in contact with the object to be welded without any gap before pressing the electrode (hereinafter, referred to as “fixed electrode”)
This position is called a fixed electrode contact point). Also, if the movable electrode does not stop at the point where it comes into contact with the workpiece, the electrode and the workpiece will be adversely affected. Therefore, the position where the electrode contacts the workpiece (hereinafter referred to as the movable electrode contact point). It is necessary to know in advance.

However, when welding is performed continuously, the above-mentioned fixed electrode contact point and movable electrode contact point constantly change due to electrode wear. In addition, the welding arm attached to a robot or the like has a limit in securing the rigidity of the gun body due to the limitation of the payload of the robot or the like. .

If the thickness of the workpiece is extremely small, the fixed electrode contact point and the movable electrode contact point substantially coincide with each other.
When this point is set as the theoretical pressing point, the gun arm bends due to the pressing force (several hundred kgf). As shown in FIG. 4, the actual pressing point Zt is equal to the gun arm bending amount ΔZ from the theoretical pressing point Zj. The position is shifted only by

Therefore, it is necessary to detect the fixed electrode contact point, the movable electrode contact point, the theoretical pressure point, and the actual pressure point by any method.

Further, the weight of the movable portion of the movable electrode of the welding gun causes an error in the electrode pressing force depending on the position of the gun, so that the electrode pressing force becomes unstable.

Conventionally, the amount of deflection of the gun body during pressurization (actual press point) is actually measured using a measuring instrument, and thus the method of the present invention is effective. In addition, the effect of the gun posture on the electrode pressing force has not been conventionally considered. Therefore, the present invention has been made to solve the above problems.

FIG. 1 shows a welding gun 2 shown in detail in FIG.
Shows an electrode position detecting device 1 for detecting the position of each electrode of
FIG. 8 shows a spot welding apparatus W in which the electrode position detecting device 1 is used. As shown in FIG. 1, the electrode position detecting device 1 includes a welding gun 2 and a control system 5. In addition, as shown in FIG.
Has an electrode position detecting device 1 and a welding robot R including a welding gun 2 as hardware. The spot welding apparatus W in FIG. 8 illustrates a robot of a type having a separate welding transformer TR disposed on the ground for easy understanding. The spot welding apparatus W may be one in which a compact welding transformer is attached to the welding gun 2.

As shown in FIG. 8, the spot welding device W includes a welding robot R installed on the ground and operating the welding gun 2 and a control device 50 for controlling the spot welding device W.
The control panel 50a is mounted on the front surface of the welding transformer TR, the control panel 50b is mounted on the base of the welding robot R, and the control panels 50c and 50d are mounted on the arm of the welding robot R, respectively. Various commands can be output from the control panels 50a to 50d to the control device 50.

Although not shown, the spot welding apparatus 1 supplies necessary power and fluid, an electric cable, an optical cable, a signal line for communication and control, and the like.
It has a cooling system including an interface, hydraulic and pneumatic lines suspended on overhead rails, an air conditioner, and a cooling hose that supplies a cooling liquid to the electrodes.

The control device 50 shown in FIG. 1 includes a central processing unit (hereinafter, referred to as a CPU) 52 for controlling the operation of the spot welding device W, an arithmetic device 54 capable of high-speed operation, a program necessary for the operation, and And a storage device 56 for storing data.

As shown in FIG. 8, the welding gun 2 is attached to the ends of arms having a plurality of degrees of freedom of the welding robot R, and these arms allow a pair of relatively movable welding electrodes ( The attitude of the welding gun 2 is controlled three-dimensionally so that the combination of the movable electrode 22 and the fixed electrode 24) is set at a desired initial position for spot welding.

As shown in FIGS. 8 and 9, the movable electrode 2
2 and the fixed electrode 24 are attached to the welding gun 2. A gun body 20 called a gun arm includes an arm end portion 20a, an arm base portion 20b, and an intermediate portion 20c.
Are formed in a bow or C-shape between the two. The feed mechanism 30 is attached to and supported by the arm base portion 20b. The servo motor 26 is connected to the arm base 2
0b to drive the feed mechanism 30. The movable electrode 22 can be moved in each direction of the feed direction Df of the feed mechanism 30. The fixed electrode 24 is attached to a position facing the movable electrode 22 by an arm end portion 20a.

An electrode sensor 60 that functions as a tip detector by fixing the bracket set 70 to the gun arm 20 is incorporated in the welding gun 2. An electrode holder 20d and a water jacket 20 are provided on the arm end portion 20a.
e is provided. A cooling passage through which cooling water flows is formed in the gun body 20, and a cooling hose is connected to the cooling passage. The gun body 20 also has a conductor for guiding a welding current to the fixed electrode 24.

The feed mechanism 30 includes an arm base portion 20b
, A ball screw 32 rotatably attached to the mount base 31 so as to advance and retreat in the feed direction Df, and connected to a drive shaft of the servo motor 26, and a nut member to be engaged with the ball screw 32. 33, a slide base 34 attached to the nut member 33, and an electrode holder 35 attached to the slide base 34 and formed with a cooling passage connected to a cooling passage of the gun body 20.

As shown in FIG. 10, the servo motor 26
The motor drive current I is controlled by a motor drive command C input from the CPU 52 to the interface 26b. The motor drive current I is sent from the interface 26b via the servo motor 26a according to the motor drive command C.

The motor drive current I is measured as current data Di by the ammeter 26c. Servo motor 26
The current rotation number of a is measured as rotation data Dr by the encoder 26d. This motor drive current I is
It should not be measured as the motor drive command C of the CPU 52. The current data Di and the rotation data Dr are simultaneously output to the interface 26b, and the electrode position data Dp
Is sent to the CPU 52. The current data Di and the rotation data Dr are demultiplexed. The rotation data Dr is CP
U52, the movable electrode 22 in the feed mechanism 30
Is calculated.

The current data Di is input to the CPU 52 for checking a zero torque point described later.

As shown in FIG. 10, the servo motor 26a
Is connected to the ball screw 32, rotates the ball screw 32 with the driving torque Td, drives the nut member 33,
As a result, the slide base 34 moves, and the movable electrode 22
Is moved in the feed direction Df. Assuming that the axis of the rectangular coordinate system set on the gun arm 20 is Z, the movable electrode 22 (more specifically, the tip end thereof) plays along the Z-axis or reproduces from the initial position Z = 0 to a constant forward position Z = It is sent up to Zi (Zi> 0).
The movable electrode 22 contacts the object Ob (for example, a point to be welded or the fixed electrode 24), and generates a pressing force on the object Ob.

When the object Ob is pushed forward by a small distance ΔZ until it stops at the position Z = Zj (Zj> Zi) where the object Ob is pushed, the force F is balanced (for example, the fixed electrode 2).
4 or by slightly bending the arm end portion 20a of the gun arm 20).

As shown in FIG. 11, the driving torque Td is
It increases as the motor drive current I increases.

Since the feed mechanism 30 has weight, mechanical resistance, and backlash, the friction ΔTd of the driving torque T is consumed as a loss, and the remainder (Td−ΔT
d) becomes the pressing force F. Then, the feed mechanism 30 corresponds to the number of steps of increasing the current and determines a predetermined zero pressure point (F
= 0). The zero pressure point (F = 0) is a strict zero torque point (T = T) corresponding to the zero pressure point (F = 0).
0), the CPU 52 determines the motor torque T (as used herein) as the motor torque T (as used herein) from the magnitude of the drive torque Td clearly and effectively as a fraction (Td−ΔTd). ) Is preliminarily taught to the CPU 52 so that it can be recognized.

As shown in FIG. 9, the movable electrode 22 has an electrically conductive adapter 22a screwed into the electrode holder 35 at the base end of the movable electrode 22, and an adapter 22a.
The electrode tip 22a has a pointed or rounded electrode tip 22b to be finished.

FIG. 12 is a sectional view of an end portion of the movable electrode 22. The adapter 22a has a supply and return cooling passage 22c formed therein and a radial electrode tip 22c.
It has an outer peripheral surface 22d tapered toward the inside of b at the end. The electrode tip 22b is formed with a hole or a recess 22e for circulating the cooling liquid, and the hole or the recess 2e is formed.
2e has an inner peripheral surface 22f which is forcibly fitted on the outer periphery 22d of the adapter 22a and which tapers radially outwardly to achieve a watertight condition.

The position of the movable electrode 22 is represented by the Z-axis coordinate of the end (ie, the top profile) of the electrode tip 22b detected by the electrode sensor 60. The dressed electrode tip 22b applies the movable electrode 22 to the fixed electrode 24 with the largest reference force (e.g., 400 kgf) allowed in relation to the servomotor 26 rating, shape, and dimensions of the adapter 22a and electrode tip 22b. , Hereinafter referred to as the maximum pressurizing force).

The fixed electrode 24 is composed of an electrically conductive adapter 24a screwed to the electrode holder 20d and a pointed or round electrode tip 24b forcibly finished to the adapter 24a.

When the fixed electrode 24 is present, after the contact with the movable electrode 22, its position is represented by the Z-axis coordinate of the end of the electrode tip 24b.

The coolant from one hose is applied to the electrode tip 2 so that the welding voltage is relatively low without any extra insulation.
Circulated through 2b and 24b back to the other hose.

The electrode sensor 60 is a non-contact type sensor, and includes a radiator fixed to the arm base portion 20b for irradiating an infrared beam B, a transmitter or a projector (hereinafter collectively referred to as a "projector"). 61, a coherent or non-coherent light orthogonal to the feed direction Df of the movable electrode 22, and a photoelectric diode or transistor, an optical coupling element, or a photodetector fixed to the arm base portion 20b to receive the beam B from the projector 61 (Hereinafter collectively referred to as a “light receiver”) 62.

The light projector 61 is connected to a signal line 61 a of a drive command output from the control device 50, that is, from the CPU 52.
Is controlled via The light receiver 62 includes a signal line 62a that sends detection data Dt (see FIG. 1) to the control device 50.
To input and output the data to and from the CPU 52.

The light receiver 62 detects a sharp or rounded or distorted end of the electrode tip 22b of the movable electrode 22. This detection is performed, for example, when most of the light of the beam B is blocked by the end of the electrode tip, and the detection data Dt is input to the CPU 52. This is processed to detect the blocking electrode tip end. When the electrode tip end is detected, the calculated current feed position is read, whereby the current position of the electrode 22 is determined and detected with respect to the Z-axis coordinate of the detected electrode tip end.

The light projector 61 and the light receiver 62 are both mounted on the bracket set 70 in the rectangular coordinate system set for the gun 2.
Fixed by As illustrated by FIG.
The beam B from the light projector 61 is defined by the coordinates Z = Z
It intersects the Z axis vertically at a reference point having r (0 <Zr <Zi).

As shown in FIG. 9, the bracket set 70
Are fixed to the arm base portion 20b, are arranged at a distance from each other in a direction perpendicular to the feed direction Df of the movable electrode 22, and are fixed to the arm base portion 20 by screws 72a, 71a.
b, a pair of substantially C-shaped support pieces 71, 72
The one support piece 71 supports the light projector 61, and the other support piece 72 supports the light receiver 62.

The movable electrode 22 is connected to the arm base 20b.
From the initial position Z = 0 (FIG. 10) located behind the sensor 60 across the arm dimension H (FIG. 1) between the front surface of FIG. 9 and the tip end of the fixed electrode 24, FIG.
= Zj (FIG. 10). This stroke is greater than the arm spacing of the welding gun 2 (between 20a and 20b).

FIG. 13A illustrates the basic use of the principle of electrode position detection and the principle of measurement of the mutual electrode distance by the electrode position detecting device 1 of FIG. 1, and FIG. 9 illustrates the application of the principle of electrode position detection to measurement. In FIG. 13A, the movable electrode 22 (more specifically, a new electrode tip 22b) has three positions. Position (i) This position is the first zero feed point now assumed to be identical to the first point Z = 0. Position (ii) The round tip end blocks beam B at reference point Z = Zr. Position (iii) The end of the electrode tip comes into contact with the round tip of the fixed electrode 24 (of the new tip 24b) at the initial contact point Z = Zi1 without pressure. This non-pressurized contact state is first detected at the maximum pressing force F (FIG. 11), which may be the maximum pressing force, and then slightly returned to the zero torque point (T =
0) is detected by the CPU 52.

The movable electrode 22 is sent by a sending mechanism 30.

First, at the distance Zr from the position (i) to the position (ii), the end of the electrode tip is detected by the light receiver 62 (FIG. 9) and recognized by the CPU 52 (FIG. 1). The CPU 52 calculates the current calculated feed Fr1.
And the current electrode position is Zr, and the additional distance from position (ii) to position (iii) is Lr1 (= Zi
1-Zr). The state of the non-pressing contact already described is such that the CPU 52 sets the current calculated feed Fi1 (= Fr1 + Lr) as the current electrode position Zi1.
When reading 1), the CPU 52 detects it.

As a result, before the next welding, the CPU 52 sets the current distance between the movable electrode 22 and the fixed electrode 24 at the reference position Zr (finished for the unused tip 24b) as a reference. In order to reach the point Zr and the reference distance Lr1 (= Zi1-Zr), the required feed amount Fri (= Zr) of the movable electrode 22 (the unused tip 22b is finished) is notified.

In FIG. 13B, the movable electrode 22 that has been deformed or worn by one or more welding operations again has three positions. Position (iv) The electrode 22 has a gap dZ1 corresponding to the degree of its deformation.
And wait at the current zero feed point (-dZ1) shorter than or smaller than the initial feed point Z = 0. Position (v) The end of the distorted electrode tip blocks beam B at reference point Z = Zr. Position (vi) The end of the electrode tip has a distorted tip of the fixed electrode 24 at the current contact point Z = Zi2 (= Zi1 + dZ2) farther from the initial contact point Zi1, with a gap dZ2 corresponding to the degree of deformation of the electrode 24. It comes into contact with the end without pressure.

The movable electrode 22 is first sent to a distance Zr + dZ1 from the position (iv) to the position (v). The tip end of the chip is detected by the light receiver 62, and when the current calculated feed Fr2 is read as the electrode position being Zr, the CPU ends.
52 detects.

Additional distance L from position (v) to position (vi)
In r2 (= Zi2-Zr), the CPU 52
The current calculated feed Fi2 (=
When reading (Fr2 + Lr2), the CPU 52 detects the state of non-pressing contact. As a result, the CPU 52
Indicates a feed Fr2 (= Zr + dZ1) required for the movable electrode 22 (finished for the used tip 22b) to reach the reference point Zr and the reference distance Lr2, and the movable electrode 22 and the fixed electrode at the reference position Zr. 24 (finished for used tip 24b).

The reference position Zr is common, and related data (including at least Fr1, Fi1, or Lr1, and Fr2, Fi2, or Lr2) is stored in the storage device 56 (FIG. 1). The respective degrees of deformation of 22b and 24b,
In order to determine dZ1 and dZ2, arbitrary set data can be read and processed for various applications such as correction or correction of a feed distance, an electrode position or a mutual electrode distance.

In the electrode position detecting device 1, the movable electrode 2
2 functions as a scaleless reference measure having a reference scale defined thereon by the beam B from the projector 61. When sent beyond the reference point Zr, the measure has a defined length. In addition, the spot welder W of FIG. 9 is an equalizer that automatically corrects the electrode position to the position where the workpiece deviates from the welding point of the workpiece (the fixed electrode 24 is fixed at the level “fixed electrode contact point” below the welding point). Means required for contact without any gap and for bringing the movable electrode 22 into contact with the movable electrode 22 at a level “movable electrode contact point” above the welding point without pressurization are not provided.

The welding gun 2 has a weight designed in consideration of the nominal allowable load of the robot arm.
Has a rigidity and strength to withstand a pressing force F acting from the side of the movable electrode together with a slight increase in bending due to an increase in the pressing force during welding. Therefore, FIG.
As shown in the figure, a deviation of the position of the welding point occurs.
The weld point is assumed to be of zero thickness because the movable electrode contact point substantially coincides with the fixed electrode contact point. And it is indicated by the point Z = Zt as a theoretical pressure point.

The gun arm 20 has a pressing force F (several hundred kgf).
, So that the theoretical pressing point Zt is located at a small distance ΔZ (see FIG. 10) from the other point Z.
shift to j. Further, the pressing force F slightly changes with respect to the attitude of the welding gun 2. The present embodiment can cope with such a deviation in force position and a change in force in addition to the basic detection and correction of the electrode position.

FIG. 2 shows a flowchart of the basic detection and correction operation by the electrode position detecting device 1 of FIG.

The welding gun 2 has a new (tip 22b) movable electrode 22 and a new (tip 24b) fixed electrode 24.

In step S 1, the drive command C is output from the CPU 52 of the control device 50 to the servo motor 26 together with command data defining the pressing force output from the movable electrode 22. When the romance C is given, the servo motor 26 moves the movable electrode 22 at a low speed in the compression direction, that is, the feed direction Df (FIG. 10).

In step S2, the tip end of the movable electrode 22 is detected by the electrode sensor 60 used as a tip detector (Zr in FIG. 13A). As soon as it is detected, the current position Fr1 of the movable electrode 22 is stored in a storage area of the storage device 56 (hereinafter, referred to as the storage device 1).

In step S3, as shown in FIG. 5, the movable electrode 22 is moved at a high speed (by the distance Lr1) until it comes into contact with the fixed electrode 24.

In step S4, the movable electrode 22 comes into contact with the fixed electrode 24, and the finished electrode tips 22b, 24b on both electrodes 22, 24 are aligned with the ends.
The movable electrode 22 is pressed against the fixed electrode 24 with the maximum pressing force F0.

In steps S5 to S7, the servo motor 2
6 is gradually reduced from the state of step S4. The pressure F0 of the movable electrode 22 is reduced, and when the pressure F0 is reduced from ΔF to zero,
(FIG. 13A) is detected (as if Fi1 is sent) and stored in another storage area of the storage device 56 (hereinafter referred to as the storage device 2). Thus, the storage device 1 and the storage device 2 store the data Fr1 and Fi1 of the positions Zr and Zi1 of the electrode tip end of the new movable device 22 and the fixed electrode 24.

In step S8, the servo motor 26 moves the movable electrode 22 at a high speed to return to the predetermined original position. Thereby, the arm interval H (FIG. 1) is opened. The aforementioned steps S1 to S8 may be preferably performed twice to update the data of the storage device 1 and the storage device 2 in order to completely dress the electrode chip.

When spot welding is performed several times, the electrode 2
Steps S <b> 9 to S <b> 11 are processed because the ends of the chips 2 and 24 are worn or deformed. There, data Fr2 (FIG. 13B) on the position Zr of the movable electrode 22 detected by the end detector 28 is stored in a storage area of a storage device 56 (hereinafter, referred to as a storage device 3). The data Fi2 on the contact point Zi2 of the movable electrode 22 is stored in the previous storage device 5.
6 (hereinafter referred to as the storage device 4) in another storage area.

In step 12, the data stored in the storage devices 1 to 4 is processed by the CPU 52 for calculating the wear amounts dL1 and dL2 (FIG. 5) of the movable electrode 22 and the fixed electrode 24 as follows. Is done.

The data stored in the storage devices 1 to 4 is fed from the zero feed point or the original position of the movable electrode 22 (Fr1, F2 in FIGS. 13A and 13B).
i1, Fr2, Fi2) or displacement. Therefore, the data (Fr) in the storage device 3
2) is subtracted from the data (Fri) of the storage device 1 to determine the wear amount dL1 (= dZ1) of the movable electrode 22, and the data (Fi2) of the storage device 4 is the total wear of the movable electrode 22 and the fixed electrode 24. It is subtracted from the data (Fr2) in the storage device 3 to determine the quantity dL1 + dL2. Further, the wear amount dL1 of the movable electrode 22 is determined by the total wear amount dL1 to determine the wear amount dL2 (= dZ2) of the fixed electrode 24.
+ DL2.

In step S13, the calculated wear amount d
L1 and dL2 are used in the control device 50, for example, to correct a command C for positioning the movable electrode 22 or to correct (trajectory) teaching data of the robot R.

In other words, the correction and correction of the wear amounts dL1 and dL2 are performed by the movable electrode 22 (see FIG.
It is created from the command data of the welding posture of the zero balance point Zj) or the position of the locus determined by the robot R. Such detection allows accurate detection of electrode wear, free of errors due to repeated positioning or mechanical stiffness and the accumulation of bending following the backlash of the robot R. Such an accurate correction will improve the quality of the weld.

After the replacement of the electrode tip in the welding operation, the robot R can be moved from the same operation position to the position where the pressure can be applied with a minimum pressure, so that the recovery time of the welding operation can be reduced. Further, various effects such as no space for installing the wear amount detecting device and no cost are obtained.

The electrode tips 22b and 24b (FIG. 12)
Each is a consumable and requires frequent replacement. These are inserted into the chip adapter 22a or 24a. Inadequate finishing of the electrode tip results in unexpected electrode length changes. Since the tip of the electrode tip is moved each time welding is performed, when it is pushed by the tip of the opposing electrode, it causes a wear detection error. This embodiment can address this problem.

Further, the electrode position detecting device 1 can accurately and quickly detect the bending of the welding gun 2 and can be applied to quantitative correction of the electrode position with respect to the bending of the welding gun 2.

FIG. 6 is a graph showing the amount of deflection of the gun observed in such an application of the electrode position detecting device 1.

The movable electrode 22 comes into contact with the fixed electrode 24 many times with different pressures F. Each time, pressure data (first time F <200Kg, second time F <300Kg,
The third F <400Kg and the fourth F <500Kg) and the data set (m1, m2, m3 and m4) of the storage device 56
(The first time less than 0.2 mm ΔZ, the second time less than 0.3 mm, the third time less than 0.4 mm, and the fourth time less than 0.5 mm).

The plurality of data sets collected in this manner are read into the CPU 52, and are read by the welding gun 2
(ΔZ = M (F) = b1F + b2) is processed by a least squares method combined with a linear regression equation to evaluate a representative of a linear function M representative. Here, b1 is a constant as the slope dM / dF, and b2 is a constant as the amount of deflection ΔZ. At least two data sets are processed successfully to determine the constants b1 and b2 in the individual cases, so that the function M has an advantageous linearity. The bending amount ΔZ of the welding gun with respect to an arbitrary pressing force F may be evaluated inside or by interpolation of the data along the evaluated straight line M, and for correcting the electrode position, correcting the bending of the welding gun. May be used.

FIG. 3 is a flowchart showing the operation of the electrode position detecting device 1 applied to the correction of the electrode position with respect to the bending of the welding gun.

Such processing is performed for the following reason.

Generally, the electrodes used in the resistance spot welding machine are consumables, and are supposed to be frequently replaced.
The electrode tip is attached by driving a tapered cylindrical electrode tip into an electrode holder that fits the electrode tip. Therefore, if the insertion of the electrode tip is not easy, the electrode tip will sink into the electrode holder every time pressurization is repeated, and an error will occur in the later detection of the amount of electrode wear.

The processing to be described below relates to a method for detecting the amount of deflection of the resistance spot welding gun and a method for correcting the amount of deflection. This method quantitatively, accurately and quickly detects the amount of arm deflection of a resistance spot welding gun, which has conventionally relied on empirical and estimated values.

A new movable electrode 22 (upper end 22b) and a fixed electrode 24 (upper end 24b) which are not yet used for welding are attached to the welding gun 2.
The CPU 52 executes the method just described (step S1 in FIG. 2).
And S2) have the data Fr1 (FIG. 13A) of the position Zi1 of the movable electrode 22 stored in the storage device 1 and store it in the storage device 2 in the method just described (in steps S3 to S8 in FIG. 2). Fr1 of zero pressurization point Zi1 stored in
(FIG. 13A). Therefore, the tips 22b and 24b of the electrode tips are adjusted to the ends (at the maximum pressing force F0 in step S4).

In step S21 of FIG. 3, the drive command C includes command data defining the pressing force output from the movable electrode 22,
Is output to The servomotor 26 moves the movable electrode 22 at a low speed in the compression direction according to the given command C.

In step S22, the tip end of the movable electrode 22 is detected by the electrode sensor 60 functioning as a tip detector (Zr).

In step S23, the additional feed amount Lr1 for the movable electrode 22 required to reach the contact point Zi1
The contact position with the fixed electrode is calculated based on (FIG. 13A).

In step S24, the movable electrode 22 is moved at a high speed (at the feed Lr1) until it comes into contact with the fixed electrode 24.

At steps S25 to S27, the movable electrode 2
The electrode 22 is configured such that the electrode 22
With the applied pressure F (which is initially set to the maximum F0 and then gradually reduced), as shown in FIG. 10, stops at the pressurized contact point Zj, and the electrode 22 is slightly (excess feed). It is moved to push forward against the fixed electrode 24 so as to advance (by ΔZ). The pressing force F balances the reaction force and the bending of the gun arm 20.

In step S28, the CPU 52 causes the storage device 56 to store the data on the pressing contact point (Zj) together with the data on the pressing force F (such as m4 in FIG. 6).
The combination of (i1 + ΔZ) is stored.

At step S29, at step S2
The processing of 5 to S28 is repeated once or more. In each round, a changing (gradually decreasing) pressing force F is applied from the beginning, and the changing pressing force F (m3, m2 or m1 in FIG. 6) is applied.
Along with data (Fi1 + ΔT) on various contact points (Zj) in the storage device 56.

In step S 30, the stored data set (on F and Zj) is read by CPU 52. They are processed to determine the stiffness of the welding gun 2 with respect to the welding gun deflection function M (FIG. 6) or its constants b1 and b2, for example using a linear regression equation;
The result data is stored in the storage device 56.

In step S31, the servo motor 26 moves the movable electrode 22 at a high speed to return to the original position.
After several spot welding operations, the control flow of the flowchart proceeds from step S32 to step S34, in which data Fr2 (FIG. 13B) on the position Zr of the movable electrode 22 detected by the end detector 28 is obtained. Data Fi2 on the zero press point Zi2 of the movable electrode 22 and the fixed electrode 24 is stored in another storage area of the storage device 4, and stored in the storage area of the storage device.

In step S35, the data (FIG. 13A and FIG.
(B1, Fr1, Fi1, Fr2, Fi2) are the wear amounts dL1 and dL2 of the movable electrode 22 and the fixed electrode 24 in the described method (as in step S12 of FIG. 2).
Processed by CPU 52 to calculate (FIG. 5).

In step S36, in consideration of the bending M of the welding gun which changes depending on various pressing forces F, for example, the command C for positioning the movable electrode 22 or the (trajectory) teaching to the robot R is performed. To correct the data,
The control unit 50 calculates the wear amounts dL1 and dL2 calculated together with the stored data (in step S30) on the gun rigidity.
Is used.

In other words, due to the welding position of the movable electrode 22 and the trajectory determined by the robot R, the electrode 2
The corrections for correcting the wear amounts dL1 and dL2 of Nos. 2 and 24 and the deflection M of the welding gun 2 or the gun arm 20 are made from the command data of the position (pressed toward the balancing point Zj in FIG. 10).

When the measurement is performed and correction is performed, the electrode tip can be sufficiently inserted, so that the amount of wear of the electrode can be detected with high accuracy. Further, no error occurs in the electrode wear amount due to the subsequent pressurization. Therefore, it is possible to detect and correct the deflection amount of the gun arm, which cannot be performed conventionally. Further, since the optimal amount of deflection of the gun arm can be corrected in accordance with the pressing force, further improvement in welding quality can be expected.

Steps S21 to S31 in FIG. 3 may be executed between steps S8 and S9 in FIG. In this case, the pressing force F used in the next welding operation is
Extra feed (ΔZ), full feed (Fi1 + Δ
Z) or the balance point Zj may simply be stored in the storage device 26 or read for direct use in determining the electrode feed of the welding operation.

The pressing force F changes with the posture of the welding gun 2 having the distributed weight. For example, the pressing force F
The fixed electrode 24 on the arm end portion 20a has a standard gun position that supports the downward pressure F from the movable electrode 22 and the load fraction from the arm base portion 20b having the feed mechanism 30; The electrode 24 changes between an opposing gun position that receives an upward pressure from the movable electrode 22.

FIG. 7 is a diagram showing a measurement result of a change in the pressing force F depending on the posture of the welding gun 2 (weight 20 kg) set substantially horizontally on the rotation axis of the robot arm.

The attitude is changed from the normal position of zero radians to each opposite half radian to obtain seven data sets n0-n6.

A sine curve N is described using a regression equation y = Asin (x) + B and the least squares method. Here, y is the gun bending, x is the gun posture, A is the gun weight, and B is a constant for the magnitude of the effective torque T (FIG. 11).

The electrode position detecting device 1 shown in FIG. 1 corrects the electrode position in consideration of the attitude of the welding gun 2 as follows.

First, the welding gun 2 is set to a normal position in which the movable electrode 22 has a feed direction Df in which the movable electrode 22 is oriented substantially vertically downward, and the first data of the deflection of the gun 2 is explained. (Step S in FIG. 3)
21 to S28) and stored in the storage device 56.

Next, the welding gun 2 moves the movable electrode 22 in a feed direction D in which the movable electrode 22 is oriented substantially vertically upward.
f (FIG. 9) and the second data of deflection of the gun 2 is similarly detected and stored.

The first and second data are CP
The upper limit value and the lower limit value corresponding to the first and second data are read by U52 so that the sinusoidal curve represents the component of the weight load pressed on the pressing point Zj (FIG. 4) in an arbitrary posture of the welding gun 2. Sinusoidal curve (y = Asin
It is processed by the regression equation calculation of (x) + B).

Therefore, in welding, the pressing force F is corrected in order to correct the load components in various positions of the welding gun 2, and a desired pressing force is applied to the welding point, so that the welding quality is reliably improved. be able to.

In the present embodiment, the CPU 52 directly measures the electrode wear, corrects the electrode position, and performs direct quantitative correction for the deflection of the welding gun 2 and the change in the pressing force due to the posture of the welding gun 2. The movable electrode 22 is used as a reference scale for adjusting the scale.

As is apparent from the above description, the present embodiment accurately detects the amount of electrode wear by avoiding errors such as repeated positioning, bending of the welding gun according to mechanical rigidity, and backlash of the robot. Can be. The resulting correct correction will improve weld quality.

The present embodiment can cope with the problem of the electrode tip, which is consumed every time welding and requires frequent replacement, and may have insufficient finishing because no unexpected change in electrode length occurs.

This embodiment uses the maximum pressure before detecting the amount of electrode wear, achieves a thorough finishing, enables accurate detection of electrode wear, and detects detection errors resulting from repeated compression. Is removed, resulting in improved welding quality.

Further, in the present embodiment, the electrode position can be quantitatively corrected for the bending of the welding gun, and accurate correction for the bending can be performed.

Further, in this embodiment, the load components of various gun postures can be corrected, and a desired pressing force acting on the welding point can be obtained, so that the welding quality can be surely improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing an electrode position detecting device of the present invention.

FIG. 2 is a flowchart showing the operation of the apparatus of FIG.

FIG. 3 is a flowchart showing the operation of the apparatus of FIG.

FIG. 4 is a diagram for explaining a deviation of an electrode position.

FIG. 5 is a diagram provided for describing determination of the amount of electrode wear.

FIG. 6 is a graph showing a change in deflection of a welding gun.

FIG. 7 is a graph showing a variation of a welding gun posture and a pressing force.

FIG. 8 is a perspective view of a spot welding machine equipped with the electrode position detecting device of the present invention.

9 is a detailed view of a welding gun in the spot welding machine shown in FIG.

FIG. 10 is an electric circuit diagram of a servomotor of the welding gun of FIG. 9;

FIG. 11 is a graph showing a change in torque of the servo motor of FIG. 10;

FIG. 12 is a cross-sectional view of a distal end portion of a welding electrode of the welding gun of FIG. 9;

FIG. 13 is a diagram showing the principle of electrode position detection.

FIG. 14 is a diagram provided for explanation of a conventional electrode wear amount detection method.

FIG. 15 is a diagram provided for explanation of a conventional electrode wear amount detecting method.

FIG. 16 is a diagram provided for explanation of a conventional electrode wear amount detection method.

FIG. 17 is a flowchart showing a process of the conventional electrode wear amount detecting method shown in FIG.

FIG. 18 is a flowchart showing a process of the conventional electrode wear amount detecting method shown in FIGS. 15 and 16;

[Explanation of symbols]

 Reference Signs List 10: wear amount detection jig, 20: welding gun, 22: movable electrode, 24: fixed electrode, 26: servomotor, 30: feed mechanism, 50: control device, 60: electrode sensor, 61: light emitter, 62: light receiving vessel.

Claims (24)

[Claims] An electrode position detecting device for a spot welding machine applied to a spot welding machine in which a welding robot operates a welding gun having a pair of relatively movable welding electrodes. An arbitrary coordinate system is defined, and cooperates with a sensor defined in the coordinate system to detect a movable electrode moved to an arbitrary position and the sensor to detect an arbitrary position of the movable electrode with respect to the welding gun. An electrode position detecting device for a spot welding machine, comprising: a position detector. 2. The sensor according to claim 1, wherein the sensor detects a tip of the movable electrode, and the arbitrary position of the movable electrode is a tip of the movable electrode in the welding gun. The electrode position detecting device for a spot welder as described in the above. 3. The welding gun has a feed mechanism for feeding the movable electrode in a feed direction, a base part supporting the feed mechanism, and an end part supporting another welding electrode with respect to the movable electrode. A gun arm, wherein the sensor is fixed to a base portion of the gun arm and projects a light beam that intersects a feed direction of the movable electrode; and 3. The electrode position detecting device for a spot welding machine according to claim 2, further comprising: a light receiving device. 4. The welding gun according to claim 1, wherein one of the supporting pieces supports a projector and the other supporting piece includes a pair of spaced-apart supporting pieces supporting a light receiver, and a base portion of the gun arm. The electrode position detecting device for a spot welder according to claim 3, further comprising a bracket fixed to the electrode. 5. The position detector, comprising: a feed mechanism fixed to the welding gun and feeding the movable electrode; a servomotor driving the feed mechanism; and controlling the servomotor to determine a position of the movable electrode. The electrode position detecting device for a spot welding machine according to claim 1, further comprising a control device for detecting. 6. The spot welding machine according to claim 5, wherein the control device recognizes a state of non-pressurized contact between a movable electrode and a fixed electrode attached to the welding gun. Electrode position detector. 7. The control device controls a feed of the feed mechanism, and moves the movable electrode to the arbitrary position between a movable electrode attached to the welding gun and a fixed electrode before spot welding. The first feed, the second feed in which the movable electrode is in a non-pressure contact state before spot welding, the third feed in which the movable electrode moves to the arbitrary position after spot welding
A movable electrode and a fixed electrode based on at least two of a fourth feed, a first, a second, a third, and a fourth feed in which the movable electrode is brought into a non-pressurized contact state after spot welding. The electrode position detecting device for a spot welding machine according to claim 6, wherein one of the following modifications is recognized. 8. The electrode position detecting device for a spot welding machine according to claim 7, wherein the control device controls a feed of a feed mechanism based on the deformation. 9. The control device according to claim 6, wherein the control device controls the movable electrode so as to apply a pressing force on the fixed electrode before the movable electrode enters a state of no pressure contact. Electrode position detector for spot welders. 10. The method according to claim 1, wherein one of the movable electrode and the fixed electrode includes an electrode member connected to the feed mechanism, and an electrode tip mounted on the electrode member. Item 10. An electrode position detecting device for a spot welder according to Item 9. 11. The control device controls a feed amount of the feed mechanism, a first feed amount at which the movable electrode is brought into a non-pressure contact state, the movable electrode acts on the fixed electrode, A second feed amount that is moved so as to have a pressing force of a magnitude balanced with the reaction of the fixed electrode; and a pressing force of a magnitude different from the magnitude that the movable electrode acts on the fixed electrode and balances with the reaction of the fixed electrode. The electrode position detecting device for a spot welding machine according to claim 9, wherein the bending of the welding gun is recognized based on the third feed amount to be held and the first, second, and third feed amounts. 12. The apparatus according to claim 11, wherein the control device controls a feed amount of the feed mechanism based on the bending. 13. The welding device according to claim 13, wherein the first bending of the welding gun having a first direction, the second bending of the welding gun having a second direction different from the first direction, the welding. 12. The method of claim 11, further comprising recognizing an influence of a direction of the bending of the welding gun based on the first and second bendings of the gun.
4. The electrode position detecting device for a spot welder according to claim 1. 14. The electrode position detecting device according to claim 13, wherein the control device controls a feed amount of a feed mechanism based on the influence. 15. An electrode position detecting device for a spot welding machine applied to a spot welding machine in which a welding robot operates a welding gun having a pair of relatively movable welding electrodes, wherein the welding gun includes: An arbitrary coordinate system is defined, a sensor means determined in the coordinate system to detect a movable electrode moved to an arbitrary position, and the sensor means detects an arbitrary position of the movable electrode with respect to the welding gun. An electrode position detecting device for a spot welding machine, comprising: a cooperating position detecting means. 16. A method for detecting a position of an electrode for a spot welding machine applied to a spot welding machine in which a welding robot operates a welding gun having a pair of relatively movable welding electrodes, wherein the welding gun has a coordinate system. A sensor is fixed to the coordinate system, a movable electrode moved to an arbitrary position is detected by the sensor, and an arbitrary position of the movable electrode in the welding gun is detected by a position detector cooperating with the sensor. A method for detecting an electrode position for a spot welding machine. 17. The detection by the sensor includes detecting a tip of the movable electrode, wherein the arbitrary position of the movable electrode is a tip of the movable electrode with respect to a welding gun. Claim 16
4. The electrode position detecting method for a spot welder according to claim 1. 18. An electrode position correcting method for a welding gun of a type attached to a welding robot and driving a movable electrode by a servomotor, wherein the welding gun includes a tip detector for detecting a tip of the movable electrode. A first step of fixing and attaching; a second step of attaching a new movable electrode and a fixed electrode to the welding gun and driving the movable electrode until the tip thereof is detected by the tip detector; A third step of calculating the amount of movement from the original position until the tip is detected by the tip detector; a fourth step of continuously driving the movable electrode until it hits the fixed electrode; A fifth step of calculating the amount of movement of the movable electrode from the original position to the abutting position when the pressure is reduced by reducing the pressure of the electrode; and after the welding is performed, A sixth step of calculating the amount of movement of the movable electrode from its original position until the tip of the movable electrode is detected by the tip detector, and a seventh step of driving the movable electrode until it hits the fixed electrode. Eighth step of calculating the moving amount of the movable electrode from the original position to the abutting position when the pressing force of the movable electrode is reduced and the pressing force disappears, and each movement obtained by a new movable electrode. A ninth step of calculating a wear amount of each of the movable electrode and the fixed electrode based on the amount of movement and each movement amount obtained by the movable electrode after welding. Method. 19. The operation of abutting the movable electrode against the fixed electrode, which is performed in the fourth step, includes an operation of pressing both electrodes with a maximum pressing force within a maximum allowable pressing force of the welding gun obtained by the servomotor. The method according to claim 18, wherein the electrode position is corrected. 20. A method of correcting an electrode position for use in a welding gun of a type mounted on a welding robot and driving a movable electrode by a servomotor, wherein the wear of the movable electrode and the fixed electrode calculated in the ninth step is performed. 19. The method according to claim 18, further comprising the step of correcting the position of the movable electrode during welding based on the amount. 21. An electrode position correction method for use in a welding gun of a type mounted on a welding robot and driving a movable electrode by a servomotor, wherein a first drive is performed until the movable electrode hits a fixed electrode.
A second step of calculating the amount of movement of the movable electrode from an original position to an abutting position by pressurizing the movable electrode with a first set pressure, and a second step different from the first set pressure. A third stage in which both electrodes are pressurized again with pressure, a fourth stage in which the amount of movement of the movable electrode from the original position to the abutting and pressing position is calculated, and the amount of movement to the abutting position and the abutting. Calculating a stiffness of the welding gun from an amount of movement to a pressurizing position. 22. An electrode position correcting method for a welding gun of a type attached to a welding robot and driving a movable electrode by a servomotor, the method comprising: performing welding at the time of welding based on the rigidity of the welding gun calculated in the fifth step. 22. The method according to claim 21, further comprising the step of correcting the position of the movable electrode at the time of pressurizing in the step (c). 23. An electrode position correcting method for a welding gun of a type mounted on a welding robot and driving a movable electrode by a servomotor, wherein the first to fourth steps are performed with the welding gun in a vertical position. Then, the position of the welding gun is changed, and the processes of the first to fourth stages are performed again, and the rigidity in consideration of the gun's own weight is calculated from the respective movement amounts obtained for the respective positions. The method of claim 21, further comprising the steps of: 24. An electrode position correcting method for a welding gun of a type which is attached to a welding robot and drives a movable electrode by a servomotor, based on a rigidity of the welding gun calculated in the step taking into account its own weight. 3. The method according to claim 2, further comprising the step of correcting the position of the movable electrode at the time of pressing during welding.
3. The method for correcting an electrode position of a welding gun according to item 3.